CHICAGO -- Eating red meat may raise a woman's risk of a common type of breast cancer, and vitamin supplements will do little if anything to protect her heart, two new studies suggest.
Women who ate more than 1½ servings of red meat per day were almost twice as likely to develop hormone-related breast cancer as those who ate fewer than three portions per week, one study found.
The other -- one of the longest and largest tests of whether supplements of various vitamins can prevent heart problems and strokes in high-risk women -- found that the popular pills do no good, although there were hints that women with the highest risk might get some benefit from vitamin C.
The meat study was published in Monday's Archives of Internal Medicine.
The vitamin study was presented at an American Heart Association conference in Chicago.
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Both were led by doctors at Harvard Medical School and were aimed at two diseases women most fear and want to prevent.
Antioxidants like vitamins C and E attach to substances that can damage cells. Scientists have been testing them for preventing such diseases as Alzheimer's and cancer.
This is the first large study to test vitamin C alone, not in combination with E or other vitamins, for heart health, said Dr. JoAnn Manson, chief of preventive medicine at Harvard-affiliated Brigham and Women's Hospital in Boston, who led the research.
More than 8,000 women were randomly assigned to take vitamin C, E or beta carotene alone or in various combinations for nearly a decade. An additional 5,442 women took folic acid and B vitamin supplements for more than seven years.
"Overall, there was minimal evidence of any cardiovascular benefit of any of these antioxidants," and people should not start or continue taking them for that purpose, Manson said.
Among the 3,000 women in the study who had no prior heart disease but three or more risk factors for it, those who received vitamin C alone or in combination had a 42 percent lower risk of stroke. Smokers taking C also had a 48 percent lower risk.
Vitamin E may give very small benefits for some women, the study suggests. Those with prior heart disease had a 12 percent reduction in the risk of new heart problems, Manson said.
"Many of these subgroup findings are intriguing. However, they need to be confirmed in other studies," Manson said. "We don't want this to be interpreted as a conclusive finding."
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What does appear conclusive is that folic acid and B vitamins "are not effective as preventive agents," said Dr. Christine Albert, who presented that portion of the study at the heart meeting on Monday. These nutrients lower homocysteine, a blood substance thought to increase heart disease risk, but many studies now call the importance of that into question.
The meat study was based on observation rather than an experiment. The Nurses' Health Study tracked the diets and health of more than 90,000 women who were 26 to 46 years old when they enrolled roughly two decades ago.
